1. Field of the invention
This invention relates to a connection terminal for a fuse used in an automobile or the like for protecting a load circuit against an excess current.
2. Related Art
A fuse element made of a copper alloy or the like has heretofore been used for protecting a circuit through which an excess current several times larger than a stationary current flows immediately after starting the operation as in a motor load circuit of an automobile. Such a fuse element integral with a terminal portion has been stamped from a copper alloy sheet.
However, such a copper alloy has a high fusion temperature, and therefore when a minimum operating current which causes the fuse to be fused, or a current close to it is caused to flow for a long period of time, the fusion portion is maintained at high temperatures for a long period of time, so that a problem with fuse characteristics has been encountered.
Under the circumstances, there has been made an attempt (as in a fuse disclosed in Japanese Utility Model Unexamined Publication No. 3-35640) in which a fuse is provided as a separate element, and only this element is made of low-melting metal. However, this increases the number of steps of the manufacturing process, and therefore is disadvantageous in that the cost becomes high.
Therefore, there has been made an attempt in which an integral construction is formed from a sheet of a metal alloy having a high fusion temperature, and contrivance is applied to a fusion portion, as shown in FIG. 5. FIG. 5(a) is a bottom view of a conventional connection terminal 51 for a fuse. The conventional connection terminal 51 for a fuse includes a fusion portion 53 of a projected configuration provided between connection portions 52A and 52B having respective curl portions 54A and 54B. FIG. 5(b) is a developed view of this connection terminal, and those portions (having a length Lc in their flat form) to be formed respectively into the curl portions are curled during a shaping operation to respectively form the curl portions 54A and 54B having a curvature as shown in FIG. 5(c) which is a front-elevational view.
In the manufacture of this connection terminal, a copper alloy sheet is stamped by a press into a developed configuration as shown in FIG. 5(b). However, it has been difficult to effect the stamping in such a manner that the fusion portion 53, as well as narrow interconnecting portions extending right and left respectively from the fusion portion 53, is stably formed, and therefore it has been difficult to reduce the percent defective of the stamping operation.
In view of this, if the fusion portion 53 as well as the right and left interconnecting portions is designed to be thick, the stability of the press-stamping operation is improved; however, the problem with fuse characteristics due to an increase of the fusion temperature is again encountered.
Another problem with this conventional construction is that heat-radiating properties are inferior. Generally, an electrical contact portion has an excellent thermal conductivity, and therefore heat is radiated from a heat-generating portion through the electrical contact portion. Because of this radiating effect, even if the above-mentioned minimum operating current causing the fuse to be fused, or a current close to it is caused to flow for a long period of time, a steady radiation, that is, heat removal, proceeds, thereby preventing the fusion portion from being heated to undesirable high temperatures.
With the conventional construction, however, an electrical connection between the connection portion 52A (52B) and a male terminal 60 is made at contact surfaces of the male terminal 60 held between bent distal ends of the curl portions 54A (54B), resiliently contacted therewith, and a bottom plate of the connection portion 52A (52B). When the male terminal 60 is repeatedly attached and detached, a problem arises with the contact condition, and a contact resistance is increased, so that a temperature rise (heat generation) due to the flowed current increases. As a result, the influence exerted on the fusion portion can not be disregarded. Under the circumstances, there has been made an attempt in which the bottom plate of each of the connection portions 52A and 52B is extended and is folded back to form a resilient piece portion; however, with this construction, although a high contact condition can always be maintained to improve the radiating effect, the material to be used is increased, thus inviting a drawback that the cost is increased.